1. Field of the Invention
The present invention relates to an antislip material ejector which ejects antislip materials between a wheel of a railcar and a rail so as to maintain frictional contact therebetween.
2. Background Art
Various kinds of apparatuses which eject antislip materials, such as grit etc. so as to avoid slipping between a wheel of a railcar and a rail and also to maintain frictional contact between the wheel and the rail have been proposed for the railcars which run on rails at high speed.
For instance, an apparatus, which comprises a grit box which stores grit, a ejection pipe which is connected to the grit box, and an air pipe which supplies air to the grit box, and which ejects grit between wheels and rails by supplying compressed air to the ejection pipe so as to push the grit out of the ejection pipe together with the compressed air is disclosed in Japanese Unexamined Patent Application Document Hei 4-310464.
In the above antislip material ejector, it is necessary to control the pressure of the compressed air which is charged in the grit box to vary the discharge rate of the grit to be ejected. However, when the pressure of the compressed air is not sufficient, for instance less than 500 kPa, power necessary for ejecting the grit decreases and the ejecting discharge rate of the grit is not stable or is not sufficient.
Furthermore, the grit and other kinds of the antislip materials tend to be compressed and also to be caked by a vibration of the railcar and the pressure of the compressed air, and therefore the discharge rate of the grit which is ejected by the same pressure of the compressed air decreases. In order not to decrease the discharge rate of the grit, it becomes necessary to adjust a needle valve of the above antislip material ejector in order to maintain a necessary ejection discharge rate of the grit.
In a case in which a plurality of ejection pipes are arranged in a single grit box, it is not possible to control the discharge rate of the ejecting particle for each of the ejection pipes, because an ejecting rate of the grit can be varied only by the pressure of the gritbox and the ejection pipes which are connected with the same gritbox are pressurized by the compressed air of the gritbox.
When a valve which controls the discharge rate of the ejecting particles is arranged in a ejection line between the gritbox and a ejection nozzle, some problems occur. For instance, the valve has parts which touch and slide past each other and these parts are damaged by the grit therebetween. Because the grit box is pressurized by the compressed air, it is necessary to make the grit box to be pressure sealed and it is also necessary to make the gritbox have high structural strength. Therefore, cost for making the gritbox thus constructed is increased.
In order to overcome the above problems, the present invention seeks to provide a antislip material ejector which ejects antislip material which is drawn from an antislip material container together with compressed air by using a venturi effect in a mixing pipe.